Non-dairy substitute for powdered milk?
I'm looking to make Peter Reinhart's recipe for Portuguese sweet bread for someone, but they have a dairy allergy and the recipe calls for powdered milk. Reinhart notes that versions made with whole milk or buttermilk don't taste as good as the powdered milk version, so I've adjusted my expectations accordingly.
I know that powdered milk is mainly used to give bread a softer texture, and a little browner crust. So what would be appropriate to achieve a similar result? And texture aside, is there anything that might help approximate the flavor of powdered milk at all?
I was thinking about trying to make a tanzhong roux? I've never tried it, but it seems easy enough. Maybe with a little extra sugar to compensate for what was in the powdered milk?
Or diastatic barley malt? I've never used it, but I think it's used for a similar purpose? How much would be appropriate?
Or could I use something like rice or almond milk? Or maybe even potato water? I don't know if that would work well with a sweet bread.